Lithospheric layering beneath northern Central Africa by S-to-P receiver functions

Abstract

Using a total of 4520 S-to-P receiver functions (SRFs) recorded by 19 broadband seismic stations belonging to the Libyan Center for Remote Sensing and Space Science and the Incorporated Research Institutions for Seismology Data Management Center, we imaged the depth of the lithosphere–asthenosphere boundary (LAB) beneath northern Central Africa. This boundary occurs over the depth range of 57–124 km which we imaged in consecutive circular bins (radius of 2°) using a high number of receiver functions. The mean depth of the discontinuity is 80 ± 17 km, which is significantly shallower than the global average of ~250 km, commonly found beneath ancient cratons. The SRFs in the study area produced 156 bins with observable arrivals from the LAB. All the stacked traces were plotted along eight latitudinal profiles from 20°N to 35°N. The observed depth of the LAB increases systematically toward the northern central part of the study area from approximately 67 km–120 km. The apparent depth of the LAB increases from 70 to 90 km from 21°N to 28°N and then further increases to 120 km from 28°N to 34°N. These depth variations are extreme beneath the northern central part of Libya. The LAB depth beneath the Hoggar volcanic province area is relatively low (~57 km) compared to other areas. This study provides new constraints on regional-scale tectonic processes such as lithospheric stretching or thinning, due to partial melting beneath the study region that may be an effect of the LAB topography in this part of northern Central Africa.